1. Field of the Invention
The present invention generally relates to an electrical connector, and in particular to a zero insertion force (ZIF) ball grid array (BGA) connector having firmly secured contact elements for effectively forming an electrical connection with pins of a chip module.
2. The Prior Art
Chip modules have been improved significantly. The amount and speed of data transferred by the chip modules has increased rapidly. Thus, a corresponding modification of a connector connecting the chip module to a circuit board is required. Corresponding examples are disclosed in Taiwan Patent Application Nos. 83207257, 83208396, 83212080 and 83212081.
FIGS. 1A, 1B, 1C and 1D show a conventional connector wherein FIGS. 1A and 1C are top views of a portion of the connector while FIGS. 1B and 1D are corresponding cross-sectional views. The conventional connector defines a number of contact receiving holes 21 in an insulative body 2 for retaining contact elements 1 therein. Each contact element 1 has an elongate body 10 comprising an engaging section 11 at one end and a retention section 12 at an opposite end. A soldering section 13 further extends from the retention section 12 and protrudes beyond the body 2 for being soldered to a circuit board 3 by solder 31. The retention section 12 comprises barbs 121 for engaging with an inside surface of the contact receiving hole 21 to secure the contact element 1 therein.
Pins 4 of a chip module are inserted into the contact receiving holes 21 of the body 2 but are initially separated from the contact elements 1. The chip module is then moved relative to the body 2 to bring the pins 4 into contact with contact elements 1 as shown in FIGS. 1C and 1D whereby the pins 4 are electrically connected to the contact elements 1.
A disadvantage associated with the conventional connector is that during the movement of the chip module, a great force is applied to the contact element 1 by the pin 4 which in turn induces a large moment at the retention section 12. The retention section 12 may thus be moved and separated from the body 2 as shown in FIG. 1D, causing damage to the solder 31 connection.
Furthermore, since the retention section 12 and the soldering section 13 are immediately adjacent to each other, a strain may be induced on the solder 31 connection due to a difference in thermal expansion of the insulative body 2 and the circuit board 3. The strain may sometimes cause breakage of the solder 31 connection. In addition, the retention section 12 and the soldering section 13 are vertically stacked on each other thereby hindering a reduction of the thickness of the insulative body 2 while maintaining the same mechanical strength when securing the retention section 12 in the contact receiving hole 21.
It is thus desirable to have an electrical connector that overcomes the problems mentioned above.